1. Field of the Invention
The present invention relates to an alternating current (AC) power supply apparatus that supplies AC voltage to a load.
2. Description of the Related Art
For example, in electrophotographic image forming apparatuses, it is necessary to prepare power supply apparatuses that supply AC high voltage to developing devices or discharging devices in photoconductor units. Japanese Unexamined Patent Application Publication No. 2001-186761 and Japanese Unexamined Patent Application Publication No. 6-197542 each disclose a high-voltage power supply apparatus that generates the AC high voltage. The high-voltage power supply apparatus described in Japanese Unexamined Patent Application Publication No. 2001-186761 includes an amplifier circuit. In the high-voltage power supply apparatus, a direct current (DC) component is cut off from an output from the amplifier circuit to transmit only an AC component and the AC voltage stepped up by a transformer is subjected to half-wave rectification. The high-voltage power supply apparatus described in Japanese Unexamined Patent Application Publication No. 6-197542 includes an LC series resonant circuit and a switching circuit. The switching circuit is switched to accumulate the inductance of the LC series resonant circuit and the accumulated energy is regenerated to control output voltage.
AC power supply circuits are reduced in size in recent years and further improvement in efficiency is desired. However, power loss in transistors is large in the amplifier circuits including the transistors, as in the power supply apparatus described in Japanese Unexamined Patent Application Publication No. 2001-186761. In contrast, although the power loss in the power supply apparatus described in Japanese Unexamined Patent Application Publication No. 6-197542 can be made smaller than that in Japanese Unexamined Patent Application Publication No. 2001-186761, the power supply apparatus described in Japanese Unexamined Patent Application Publication No. 6-197542 includes two capacitors serving as power supplies for generating positive and negative voltages of the AC voltage and the provision of the two capacitors prevents the reduction in size of the circuit.